The present invention relates to information processing systems, and more particularly, to translating circuits in digitally implemented receiving systems.
In recent years, there has been a trend in communication systems to implement a variety of the functions performed previously by analog circuits in an alternative digital configuration. This trend has been enforced by the rapid changes in solid state and digital processing technology as well as the advanced and improvements in software and microprocessor improvements which facilitate digital processing. Such advances and improvements have led to the greater use of converted analog signals into a digital format in order to improve the accuracies and quality of signal processing. There has therefore been a need for improved techniques and circuits for implementing the various digital conversions and functions that may be necessary in processing information in a digitally-implemented receiving system.
By way of example, in digitally implementing any analog receiving system, an analog signal is typically converted by an A/D converter and thereafter sampled at a given sampling rate to obtain the digital signal. The digital signal is then frequency translated by mixing to change the IF input to a lower IF baseband for further signal processing. The purpose of such frequency translation is to provide a lower IF frequency which facilitates implementation of the subsequent digital processing circuitry necessary to extract the information from the incoming IF signal. Thus, while high sampling rates may be necessary in converting and sampling the incoming analog signal in order to achieve a fairly accurate representation of the analog signal in digital form, high sampling rates tend to increase the complexity, cost and size of the digital circuitry necessary to process the converted information for subsequent use by the receiver. Accordingly, although the mathematics of frequency translation from IF to baseband may be relatively simple in theory, the actual implementation to achieve low cost circuits in a relatively non-complex manner has often been difficult. There is therefore a continuing need for systems designed to digitally implement frequency translating signal processing techniques in a digital environment to thereby enable the production of more reliable and low cost receivers.
The present invention has therefore been developed to overcome the specific shortcomings of the above known and similar techniques and to provide a digital IF translator of simplified construction for use in digitally implemented receivers.